Tissue-Removing Catheter Including Operational Control Mechanism

ABSTRACT

A tissue-removing catheter for removing tissue from a body lumen during a cutting operation includes an elongate catheter body configured for insertion into the body lumen and a tissue-removing element. A motor is operably connected to the tissue-removing element for rotating the tissue-removing element. A sensor is configured to detect a parameter of the catheter body during the cutting operation. A motor control circuit is in electrical communication with the sensor and the motor. During an operational control function, the motor control circuit is configured to receive a signal from the sensor based at least in part on the detected parameter, determine whether the received signal is indicative of inefficient movement of the tissue-removing element, and adjust a rotational speed of the tissue-removing element to increase efficiency of the tissue-removing element if the received signal is indicative of inefficient movement of the tissue-removing element.

FIELD OF THE DISCLOSURE

Aspects of the present invention generally relate to a tissue-removingcatheter for removing tissue from a body lumen including an operationalcontrol mechanism.

BACKGROUND

Vascular disease frequently arises from the accumulation of atheromatousmaterial on the inner walls of vascular lumens, particularly arteriallumens of the peripheral and other vasculature, especially peripheralarteries, resulting in a condition known as atherosclerosis.Atherosclerosis occurs naturally as a result of aging, but may also beaggravated by factors such as diet, hypertension, heredity, vascularinjury, and the like. Atheromatous deposits can have widely varyingproperties, with some deposits being relatively soft and others beingfibrous and/or calcified. In the latter case, the deposits arefrequently referred to as plaque.

Vascular disease can be treated in a variety of ways, including drugs,bypass surgery, and a variety of catheter-based approaches, includingthose which rely on intravascular debulking or removal of theatheromatous or other material occluding a blood vessel. A variety ofmethods for cutting or dislodging material and removing such materialfrom the blood vessel have been proposed, generally being referred to asatherectomy procedures. Atherectomy catheters intended to cut or excisematerial from the blood vessel lumen may employ a rotatable cuttingblade (or other tissue-removing element) which can be advanced into orpast the occlusive material in order to cut and separate such materialfrom the blood vessel lumen.

SUMMARY

In one aspect, a tissue-removing catheter includes a sensor configuredto detect a parameter of the catheter body during the cutting operationof the catheter. A motor control circuit is in electrical communicationwith the sensor and a motor. During an operational control function, themotor control circuit is configured to receive a signal from the sensorbased at least in part on the parameter of the catheter body detectedduring the cutting operation of the catheter, determine whether thereceived signal is indicative of inefficient movement of thetissue-removing element, and adjust a rotational speed of thetissue-removing element to increase efficiency of the tissue-removingelement if the received signal is indicative of inefficient movement ofthe tissue-removing element. A handle for the tissue-removing cathetermay include the electric motor, the sensor, and the motor controlcircuit.

Other features will be in part apparent and in part pointed outhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a tissue-removingcatheter;

FIG. 1A is a side view of a portion of a tissue-removing catheter as inFIG. 1, where the body has a distal portion with a bend, according toone embodiment of the present invention;

FIG. 2 is an exploded view of an exemplary distal portion of thetissue-removing catheter;

FIG. 3A is an end view of the distal portion of the tissue-removingcatheter of FIG. 1 in which the cutter is in a closed position in thecatheter body;

FIG. 3B is a sectional view along line A-A of FIG. 3A;

FIGS. 3C and 3D are views of the distal portion of a tissue-removingcatheter, where the distal portion has a locking shuttle mechanism;

FIG. 4A is an end view of the distal portion of the tissue-removingcatheter of FIG. 1 in which the cutter is in an open position outside ofthe cutting window;

FIG. 4B is a sectional view along line A-A of FIG. 4A;

FIGS. 4C and 4D are views of the distal portion of a tissue-removingcatheter, where the distal portion has a locking shuttle mechanism;

FIG. 5A is an end view of the distal portion of the tissue-removingcatheter of FIG. 1 in which the cutter is in a packing position within atip member of the catheter;

FIG. 5B is a sectional view along line A-A of FIG. 5A;

FIGS. 6 to 8 illustrate a monorail delivery system of the presentinvention;

FIG. 9A is a perspective view of a cutter of the present invention;

FIG. 9B is an end view of the cutter of FIG. 9A;

FIG. 9C is a sectional view of the cutter along line A-A of the cutterof FIGS. 9A and 9B;

FIG. 10A is a perspective view of a cutter of the present invention;

FIG. 10B is an end view of the cutter of FIG. 10A;

FIG. 10C is a sectional view of the cutter along line B-B of the cutterof FIGS. 10A and 10B;

FIG. 11A is a perspective view of another cutter of the presentinvention;

FIG. 11B is an end view of the cutter of FIG. 11A;

FIG. 11C is a sectional view of the cutter along line C-C of the cutterof FIGS. 11A and 11B;

FIG. 11D is a side view of another embodiment of a cutter, shownpartially within a catheter body;

FIG. 12 is a perspective of an embodiment of a handle for thetissue-removing catheter, including an embodiment of an operationalcontrol mechanism;

FIG. 13 is similar to FIG. 12 with a cover of the handle removed;

FIG. 14 illustrates a neutral position of a lever of the handle;

FIG. 15 illustrates a tissue-removing position of the lever of thehandle;

FIG. 16 illustrates a packing position of the lever of the handle;

FIG. 17 is an exemplary block diagram of the operational controlmechanism;

FIG. 18 is an exemplary schematic of the operational control mechanism;and

FIG. 19 is an exemplary flow diagram for a motor control circuit of theoperational control mechanism.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, an operational control mechanism for atissue-removing catheter that removes tissue from a body lumen isdisclosed. In particular, embodiments of the operational controlmechanism may be suitable for use with atherectomy catheters forremoving (i.e., excising) an atheroma (i.e., plaque) from a bloodvessel. The disclosed operational control mechanism embodiments,however, may also suitable for treating stenosis of other body lumensand other hyperplastic and neoplastic conditions in other blood vesselsand body lumens, such as the ureter, the biliary duct, respiratorypassages, the pancreatic duct, the lymphatic duct, and the like.Neoplastic cell growth will often occur as a result of a tumorsurrounding and intruding into a body lumen. While the remainingdiscussion is directed toward operational control mechanisms forcatheters for tissue-removing and passing through atheromatous orthrombotic occlusive material in an artery, it will be appreciated thatthe operational control systems may be employed with other types ofcatheters for removing and/or passing through a variety of occlusive,stenotic, or hyperplastic material in a variety of body lumens.

Referring now to FIG. 1, one non-limiting example of a suitableatherectomy catheter, for use with embodiments of the operationalcontrol mechanism disclosed below, is generally indicated at 20. It isunderstood that the operational control mechanism disclosed below may beused with other types of catheters for removing tissue from a bodylumen, and is not necessarily limited to “side cutting” atherectomy andtissue-removing catheters.

The illustrated catheter 20 comprises a catheter body 22 having aproximal portion 24 and a distal portion 26. Proximal portion 24 can becoupled to distal portion 26 with a connection assembly 27 to allowpivoting or deflection of distal portion 26 relative to proximal portion24. A tissue-removing element 28, such as a cutter, as illustrated, isdisposed within a lumen 30 of the distal portion 26, whereby the distalportion can function as a cutter housing. The tissue-removing element 28removes tissue from the lesion or obstruction. It is understood that thetissue-removing element 28 may be another type of element for removingtissue, other than the illustrated cutter, including for example, anabrasive element (e.g., a burr). The cutter 28 is typically rotatableabout an axis that is parallel to the longitudinal axis of the proximalportion 24 of catheter 20 and axially movable along the longitudinalaxis. The cutter 28 can access target tissue through a side openingwindow 32 in the distal portion 26, which is typically large enough toallow the cutter 28 to protrude through and move out of the window 32 apredetermined distance. The cutter is coupled to a handle, generallyindicated at 34 (FIGS. 12-16), through a coiled drive shaft 36.Actuation of an input device or manual actuator 38 on the handle, whichforms part of the deployment mechanism in this embodiment, can activatethe drive shaft 36 and cutter 28, and move the cutter 28 longitudinallyover a cam so as to deflect the distal portion and move the cutter 28out of cutting window 32. As explained in more detail below, camming ofthe cutter 28 can cause the distal portion 26 to pivot or deflectrelative to the proximal portion 24 so as to deflect and urge the cutterinto the tissue in the body lumen.

In some embodiments, the distal portion 26 of the catheter may be movedto an angled or offset configuration from the longitudinal axis of theproximal portion 24 of the catheter and the cutter 28. In someembodiments, the cutter 28 can also be deflected off of the axis of theproximal and/or distal portion of the catheter. Moving the distalportion 26 to an angled/offset position may cause a portion of thecatheter 20 to urge against a target tissue, may expose the cutter 28through the window 32 or both, in various embodiments.

The proximal portion 24 of the catheter body 22 may be relativelyflexible and at least a portion of the distal portion 26 may berelatively rigid. Additionally, the distal portion 26 may include aflexible distal tip member 42 at the distalmost end of the body 22. Theflexible proximal portion 24 of the catheter is typically a torque shaftand the portion of the distal portion 26 defining the cutting window 32is typically a rigid tubing. The torque shaft, which is indicated by thesame reference numeral 24, facilitates transportation of the catheterbody 22 and cutter 28 to the diseased site. The proximal end of thetorque shaft 24 is coupled to the handle 34 and the distal end of thetorque shaft is attached to the distal, rigid portion 26 of the catheter20 through the connection assembly 27. The drive shaft 36 is movablypositioned within the torque shaft 24 so as to rotate and axially movewithin the torque shaft 24. The drive shaft 36 and torque shaft 24 aresized to allow relative movement of each shaft without interfering withthe movement of the other shaft. The catheter body 22 will have thepushability and torqueability such that torqueing and pushing of theproximal end will translate motion to the distal portion 26 of thecatheter body 22.

Referring now to FIG. 1A, the catheter 20 as in FIG. 1 may have aflexible proximal portion 24 which additionally includes urging means25. As shown in FIG. 1A, urging means 25 may comprise a bent or curvedshape towards the distal end of proximal portion 24, which may help urgethe cutter 28 or other tissue-removing element toward a wall of a bodylumen to enhance treatment. Such a bend increases the working range ofthe catheter by allowing the cutter to be urged into a lumen wall acrossa wider diameter.

In other embodiments, urging means 25 may take many other suitableforms. For example, a similar result to the bend may be achieved byincluding a distal portion that is not permanently bent but that is morerigid on one side than on the opposite side of catheter body 22. Thus,when proximal tension is applied to the proximal portion 24, as whenproximal force is applied to the tissue-removing apparatus to expose thecutter 28 through the window 32, the urging means 25 will cause thecatheter body 22 to bend toward the less rigid side. The less rigid sidewill typically be the same side as the window 32, so that the window 32and/or the cutter 28 will be urged against a wall of a body lumen by thebend. In still other embodiments, a shaped element may be introducedinto catheter body 22 to act as urging means 25. Any suitable urgingmeans is contemplated.

Referring to FIG. 2, the distal portion 26 may also include a collectionchamber 53 for storing the severed atheromatous material disposedbetween the rigid portion and the distal tip 42. The distal tip member42 can have a distal opening 43 and a distal guidewire lumen that issized to allow an imaging guidewire or conventional guidewire (notshown) to be advanced distally through the tip member. For example, someembodiments may include a distal guidewire lumen having a length ofbetween about 1.0 cm and about 5.0 cm, and preferably between about 2.0cm and about 3.0 cm. Such a distal guidewire lumen may be used alone orin conjunction with a proximal guidewire lumen located on another, moreproximal, portion of the catheter 20.

A ramp or cam 44 can at least partially fit within the distal portion 26of the catheter 20. As will be described in detail below, in manyembodiments proximal movement of the cutter 28 over the ramp 44, causesthe deflection of the distal housing 26 and guides cutter out of cuttingwindow 32. Attached to the ramp 44 is a housing adaptor 46 that canconnect one or more articulation members 48 to the distal tip member 42to create an axis of rotation of the distal portion 26. The housingadaptor 46 and articulation member 48 allow the distal portion 26 of thecatheter 20 to pivot and bias against the body lumen. In the illustratedembodiment there are only one housing adaptor 46 and one articulationmember 48, but it should be appreciated that the catheters of thepresent invention can include, two, three, or more joints (e.g., axis ofrotation), if desired. Moreover, the axes of rotation can be parallel ornon-parallel with each other.

The catheter 20 can also include a shaft adaptor 50 and collar 52 tocouple articulation members 48 to the torque shaft 22. Shaft adaptor 50can connect the housing to the torque shaft 22 and the collar 52 can beplaced over a proximal end of the shaft adaptor and crimped for a secureattachment. It should be appreciated by one of ordinary skill in the artthat while one catheter embodiment has the above components that othercatheters may include more or fewer of the components described above.For example, some components can be made integral with other componentsand some components may be left out entirely. Thus, instead of having aseparate ramp 44, the ramp may be integrated with the distal portion 26to direct the cutter 28 out of the cutting window 32.

As shown in FIGS. 3-5, the cutter 28 will generally be movable betweentwo or more positions using a deployment mechanism. In the illustratedembodiment, the actuator 38 actuates operation of the deploymentmechanism, although in other embodiment, the deployment mechanism may beactuated by other actuators. In the illustrated embodiment, thedeployment mechanism allows for the cutter 28 to be selectively moveableto a stowed or neutral position (FIGS. 3A and 3B) in which the cutter isstowed in the distal portion 26 of the catheter body 22 and is notexposed through the window 32. In some embodiments, an imaging device(not shown) can be coupled to cutter 28 so as to image the body lumenthrough cutting window 32 when cutter is in the neutral position. Oncethe catheter 20 has reached the target site, the cutter 28 can be movedproximally to a tissue-removing position (FIGS. 4A and 4B), in which thecutter 28 extends through the cutting window 32 a distance L1 beyond anouter diameter D of the distal portion 26. In some embodiments, in thetissue-removing position, the cutter 28 will have deflected the distalportion 26 and the cutter's axis of rotation will generally be in linewith connection assembly 27 but angled or offset from longitudinal axisof the distal portion of the catheter body 22.

Optionally, in some embodiments, the cutter 28 can be moved to a packingposition, in which the cutter is moved distally, beyond the stowed orneutral position, so as to pack the severed tissue into the distalcollection chamber 53 (FIGS. 5A and 5B). It should be appreciatedhowever, that while the exemplary embodiment moves the cutter 28 to theabove described positions, in other embodiments the cutter can bepositioned in other relative positions. For example, instead of havingthe neutral position distal of the cutting window, the neutral positionmay be proximal of the window, and the open position may be along thedistal end of the cutting window, or the like.

Referring again to FIGS. 4A and 4B, the interaction of the components ofthe rigid distal portions 26 in one exemplary embodiment will be furtherdescribed. As shown in FIG. 4B, the cutting window 32 is typically acutout opening in the distal portion 26. While the size of the cuttingwindow 32 can vary, the cutting window should be long enough to collecttissue and circumferentially wide enough to allow the cutter 28 to moveout of the cutting window during cutting, but sized and shaped to notexpel emboli into the vasculature. The cams or ramp 44 (shown mostclearly in FIG. 4B) can be disposed in the distal portion 26 of thecatheter body 22 to guide or otherwise pivot the cutter 28 out of thecutting window 32, from the non-exposed, neutral position (FIG. 3B) tothe exposed, tissue-removing position (FIG. 4B) as the cutter 28 ispulled proximally through tensioning of drive shaft 36 via the actuator38. This operation is explained in detail below.

Referring to FIGS. 4A and 4B, a joint 49 is located proximal to thecutting window 32 to provide a pivot point for camming of the distalportion 26 relative to the proximal portion 24. The bending at the joint49 is caused by the interaction of the cams or ramps 44 with cutter 28and the tensile force provided through drive shaft 36. In the exemplaryconfiguration, the joint 49 includes a housing adaptor 46 that ispivotally coupled to the distal rigid portion 26. As shown in FIGS. 4Aand 4B, the resulting pivoting of the rigid distal portion 26 relativeto the proximal portion 24 causes a camming effect which urges thedistal portion against the body lumen wall without the use of urgingmeans (e.g., a balloon) that is positioned opposite of the cuttingwindow 32. Thus, the overall cross sectional size of the catheter body22 can be reduced to allow the catheter 20 to access lesions in smallerbody lumens. In exemplary embodiments, the distal portion 26 can deflectoff of the axis of the proximal portion 24 of the catheter 20 typicallybetween 0° degrees and 30° degrees, usually between 5° degrees and 20°degrees, and most preferably between 5° degrees and 10° degrees. Theangle of deflection relates directly to the urge. Urge, however, doesnot necessarily relate to force but more to the overall profile of thecatheter 20. For example, the greater the angle of deflection, thelarger the profile and the bigger the lumen that can be treated. Theranges were chosen to allow treatment of vessels ranging from less than2 mm to greater than 3 mm within the limits of mechanical design of thecomponents. It should be appreciated however, that the angles ofdeflection will vary depending on the size of the body lumen beingtreated, the size of the catheter, and the like.

In some embodiments, the deflection of the distal portion 26 of thecatheter 20 urges the cutter 28 into the exposed, tissue-removingposition (FIG. 4B), such that distal advancement of the entire catheterbody 22 can move the rotating cutter through the occlusive material.Because the cutter 28 is moved a distance L1 beyond the outer diameterof the distal portion 26 of the catheter 20 and outside of the cuttingwindow 32, the user does not have to invaginate the tissue into thecutting window. In some embodiments, for example, the cutter 28 can bemoved between about 0.025 mm and about 1.016 mm, and preferably betweenabout 0.025 mm and about 0.64 mm, beyond the outer dimension of thedistal portion 26. It should be appreciated that the cutter excursiondirectly relates to the depth of cut. The higher the cutter 28 moves outof the cutting window 32 the deeper the cut. The ranges are chosenaround efficacy without risk of perforation of the body lumen.

Some embodiments of the catheter 20 include a shuttle mechanism or othersimilar mechanism for temporarily locking the catheter in thetissue-removing position. FIGS. 3C and 3D illustrate such an embodimentin the neutral, non-tissue-removing position. Such embodiments generallyinclude a shuttle member 45 and a shuttle stop member 42. The shuttlestop member 42 is typically disposed at an angle, relative to alongitudinal axis through the catheter. FIGS. 4C and 4D show the sameembodiment in the tissue-removing position. When the cutter 28 is movedinto the tissue-removing position in such embodiments, the shuttlemember 45 falls into the shuttle stop member 42 and thus locks thecutter 28 in the tissue-removing position. To unlock the cutter 28, thecutter may be advanced forward, distally, to release the shuttle member45 from the shuttle stop member 42.

Some embodiments including a shuttle mechanism will also include twojoints in the catheter body 22. Thus, catheter body 22 will include thedistal portion 26, the proximal portion 24 and a middle portion. Whenshuttle mechanism is activated to expose cutter 28 through window 32,the middle portion may orient itself at an angle, relative to theproximal and distal portions, thus allowing cutter to be urged towards aside of a lumen. Such a two-jointed configuration may provide enhancedperformance of the catheter 20 by providing enhanced contact of thecutter 28 with material to be debulked form a body lumen.

Pushing the entire catheter 20 across a lesion removes all or a portionof the lesion from the body lumen. Severed tissue from the lesion iscollected by directing the removed tissue into the collection chamber 53in the tip member 42 via the cutter 28. Once the catheter 20 and cutter28 have moved through the lesion, the cutter can be advanced distally to“part off position” the lesion. During “parting off”, the cutter 28 ismoved distally from the tissue-removing position back into the cuttingwindow 32 (FIG. 3B) and to its neutral or stowed position. Thecollection chamber 53 of the tip member 42 acts as a receptacle for thesevered material, to prevent the severed occlusive material fromentering the body lumen and possibly causing downstream occlusions.After “parting off”, the cutter 28 can be moved distally to a packingposition, in which the cutter moves distally within the collectionchamber 53 to pack the severed tissue into collection chamber 53 (FIG.3B). Typically, the collection chamber 53 will be large enough to allowmultiple cuts to be collected before the catheter 20 has to be removedfrom the body lumen. When the collection chamber 53 is full, or at theuser's discretion, the catheter 20 can be removed, emptied andreinserted over the guidewire.

FIGS. 6 through 8 illustrate one exemplary monorail delivery system toassist in positioning the cutter 28 at the target site. For example, tipmember 42 of the catheter can include a lumen 54 having a distal opening43 and a proximal opening 55 that is sized to receive a guidewire,having a diameter of about 0.014 in., about 0.018 in., about 0.032 in.or any other suitable diameter.

The catheters 20 can include radiopaque markers so as to allow the userto track the position of the catheter under fluoroscopy. For example, asalready described, a point or area around or adjacent to the window 32may be made radiopaque. In other embodiments, the distal portion 26 canbe radiopaque and radiopaque markers can be disposed on the flexibleshaft 36. Typically, the markers 59 will be disposed along the top,proximal to the cutting window 32, and on the bottom of the catheter 20to let the user know the position of the cutter and cutting windowrelative to the target site. If desired, the top and bottom markers 59can be different shaped so as to inform the user of the relativeorientation of the catheter 20 in the body lumen. Because the guidewirewill form a helix in its transition from lumen 56 to tip member lumen54, the user will be able to view the top and bottom radiopaque markers59 without interference from the guidewire. Some embodiments of thecatheter 20 can also include a radiopaque cutter stop 61 (FIG. 3B) thatis crimped to driveshaft 36 proximal of the cutter that moves with thecutter so as to let the user know when the cutter 28 is in the openposition.

FIGS. 9A through 11D show some exemplary embodiments of the cutter 28.

The distal portion 60 of the rotatable cutter 28 can include a serratedknife edge 62 or a smooth knife edge 64 and a curved or scooped distalsurface 66. The distal portion 60 may have any suitable diameter orheight. In some embodiments, for example, the diameter across the distalportion 60 may be between about 0.1 cm and about 0.2 cm. A proximalportion 68 of the cutter 28 can include a channel 70 that can be coupledto the drive shaft 36 that rotates the cutter. As shown in FIGS.10A-10C, some embodiments of the cutters 28 can include a bulge or bump69 that is provided to interact with a stent so as to reduce theinteraction of the cutting edge with the stent. In any of the foregoingembodiments, it may be advantageous to construct a serrated knife edge62, a smooth knife edge 64, or a scooped distal surface 66 out oftungsten carbide.

Another embodiment of a cutter 28 shown in side view within a distalportion 26 in FIG. 11D. In this embodiment, the cutter 28 has a bevelededge 64, made of tungsten carbide, stainless steel, titanium or anyother suitable material. The beveled edge 64 is angled inward, towardthe axis of rotation (or center) of the cutter 28, creating a “negativeangle of attack” 65 for the cutter 28. Such a negative angle of attackmay be advantageous in many settings, when one or more layers ofmaterial are desired to be debulked from a body lumen without damagingunderlying layers of tissue. Occlusive material to be removed from avessel typically has low compliance and the media of the vessel (ideallyto be preserved) has higher compliance. A cutter 28 having a negativeangle of attack may be employed to efficiently cut through material oflow compliance, while not cutting through media of high compliance, byallowing the high-compliance to stretch over the beveled surface ofcutter.

Referring to FIGS. 12 through 16, one embodiment of the handle 34 willnow be described in detail. The handle 34 includes a housing 40 that issized and shaped to be held in a hand of the user. An electric motor 74(e.g., a DC motor) is contained in the housing 40, along with a powersource 76 (e.g., a battery or other source of DC power) electricallyconnected to the motor for powering the motor. The drive shaft 36 isoperatively coupled to the motor 74 when the catheter 20 is connected tothe handle 34 for driving rotation of the drive shaft and the cutter 28.In some embodiments, at maximum power the motor 74 can rotate driveshaft 36 between 1,000 rpm and 15,000 rpm or more, if desired. Themanual actuator 38 (e.g., a lever, as illustrated) on the exterior ofthe housing 40 allows the user to control operations of the catheter 20.For example, in the illustrated embodiment the lever 38 is axiallymoveable relative to the housing 40. In particular, the lever 38 ismovable to a neutral position (shown in FIG. 14), whereby the cutter 28is in its non-exposed, neutral position (FIG. 3D). To expose the cutter28 and activate the motor 74 to drive rotation of the cutter, the lever38 is moved proximally from the neutral position to a proximal,tissue-removing position of the lever (see FIG. 15) to move the cutterproximally and out of cutting window 32 (FIG. 4B) to its tissue-removingposition and simultaneously activate the motor 74. For example, proximalmovement of the lever 38 to the proximal position may actuate (e.g.,depress) an electrical switch 78 that electrically connects the powersource 76 to the motor 74. To part off tissue, the lever 38 is moveddistally from the proximal, tissue-removing position, back to itsneutral position (FIG. 14) to drive (i.e., move) the cutter 28 distallyinto the distal portion of the catheter 20 (FIG. 3D). As the lever 38 ispositioned in its neutral position, the electrical switch 78 is released(i.e., opened) so as to deactivate the electric motor 74. To pack theremoved tissue in the collection chamber 53 of the distal tip member 42,the lever 38 is moved distally from the neutral position to a distalposition, packing position of the lever (see FIG. 16) to drive (i.e.,move) the cutter 28 distally into the collection chamber and to itspacking position (FIG. 5B). It should be appreciated, while the figuresillustrate the use of an lever 38 or thumb switch, other embodiments ofthe present invention can use other types of actuators, such as separatebuttons (e.g., a close window button, debulk tissue button, and packingbutton), or the like.

During movement (e.g., advancement) of the catheter 20 across a lesionto remove occlusive material, manipulation of the catheter 20 by theuser affects the efficiency of the cutter 28 in removing the occlusivematerial. For example, if a user moves the catheter 20 distally, forexample, in the blood vessel too quickly, the cutting efficiency goesdown because the cutter 28 makes less contact with the occlusivematerial than if the catheter were moved forward at a slower rate. Whenthe catheter 20 is advanced at a slower rate, the cutter 28 makes morecontact with the occlusive material and results in uniform andunfragmented cut passes. In some cases, the inefficient cathetermovement is caused by the occlusive material itself (e.g., calcium).Current solutions for controlling inefficient catheter movement includetraining, experience, tactical feel, and visual interpretation fromangiographic imaging. For example, users may be trained to advance thecatheter 20 at a rate of about 2 mm/s, or to slow the advancement speedif chatter or vibration is felt. However, the current solutions rely onuser implementation, and do not account for inefficient user operation.

As set forth above, the catheter 20 includes one or more operationalcontrol mechanisms for automatically controlling one or more operationsof the catheter to increase cutting efficiency of the catheter in use.Referring to FIGS. 17 and 18, in an embodiment, the operational controlmechanism comprises a motor control mechanism 100 which functions toautomatically adjust the electric power (e.g., current) supplied to thecutter motor 74 from the power source 76 based on the advancement of thecatheter within the body lumen during cutting operation. For example,the motor control mechanism 100 may be constructed and/or designed todetect that the catheter (e.g., the cutter 28) is advancing (e.g.,moving distally) too quickly based on the rotational cut speed, or thatthe cutter is advancing too slowly based on the rotational cut speed (orthat the rotational cut speed is faster than necessary for optimalcutting at the current advancement speed). The motor control mechanism100 may be housed in the handle 34, as in the illustrated embodiment, orlocated elsewhere on the catheter 20. A block diagram of this motorcontrol mechanism, including the motor 74, is illustrated in FIG. 17. Asshown in FIG. 17, the motor control mechanism 100 includes a motorcontrol circuit 102 and a pulse width modulation (PWM) circuit 106connected between the power source 76 and the motor 74. In general, themotor control circuit 102 determines whether the catheter 20 is beingadvanced inefficiently, and the PWM circuit regulates the amount ofpower (i.e., current) that is supplied to the motor 74 for operating themotor and driving rotation of the cutter 28 based on the determinationmade by the motor control circuit 102.

Referring to FIG. 17, in an embodiment, the motor control mechanism 100includes a sensor 104 (e.g., an accelerometer) that senses an operatingparameter of the catheter 20, such as a parameter that is indicative ofmovement of the catheter (e.g., the advancement speed of the catheter)at some instantaneous time during the cutting operation. The sensor 104sends a signal to the motor control circuit 102 that is indicative ofthe detected operating parameter (e.g., a signal indicative of theadvancement speed of the catheter 20). The motor control circuit 102determines whether the detected operating parameter is different from athreshold that equates to an optimal parameter for a given rotationalcut speed, and outputs a signal to the PWM circuit 106 based on thesignal it receives from the sensor 104. The PWM circuit 106 regulatesthe amount of power supplied to the motor 74 based on the signal itreceives from the motor control circuit 102.

In one non-limiting example illustrated in FIG. 18, the motor controlcircuit 102 comprises a microcontroller (indicated by the same referencenumeral 102) in communication with the PWM circuit 106 and with thesensor 104. The PWM circuit 106 may comprise a microcontroller that isprogrammed to regulate the amount of power supplied to the motor 74 byoutputting a duty cycle signal to the motor based on the signal receivedfrom the microcontroller 102. It is understood that the motor controlcircuit 102 may comprise other types of devices, other than amicrocontroller, and the PWM circuit may operate suitably without theuse of a microcontroller. In the same illustrated example (or anotherexample), the sensor 104 comprises an accelerometer for sensing changesin acceleration, vibration, and/or other motions of the catheter 20 andoutputting a voltage ratio metric. The accelerometer can be positionedon the handle 34, under a distal section of the catheter body 22, or atany other suitable location. The calculated output voltage from theaccelerometer is inputted to the microcontroller 102 to determine if theoutput voltage is different from a predetermined optimal output voltage(or outside a range of a predetermined optimal range), or if the outputvoltage is equal to (or within a range of) a predetermined optimaloutput voltage. Based on this determination, the microcontroller 102outputs a signal that is inputted to the PWM circuit 106. The PWMcircuit 106 outputs a duty cycle to the motor 74 based, at least inpart, on this signal from the microcontroller 102. It is understood thatsensor 104 may be of other types and configurations without departingfrom the scope of the present invention. Other sensors that detect aparameter of the catheter that is indicative of the movement of thecatheter are within the scope of the present invention. It is alsounderstood that a motor control circuit configured to detect a parameterof the catheter and regulate power supplied to the motor, may be ofother configurations, other than illustrated and described above,without departing from the scope of the present invention.

In one non-limiting example, the motor control circuit 102 may beconfigured to increase the power (i.e., current) supplied to the motor74 a predetermined amount, to thereby increase the speed of the motor ifthe motor control circuit determines that the catheter advancement speedis at or above a predetermined threshold advancement speed level (asdetermined by the sensor output, for example) for the current rotationalcut speed. For example, the motor control circuit 102 may increase thespeed of the motor 74 to from about 7,500 rpm to about 15,000 rpm uponmaking such a determination. In such an example, the predeterminedthreshold advancement speed level is indicative of the cutter 28 beingmoved inefficiently for the current rotational cut speed (e.g.,advancing too quickly for optimal cutting, presence ofvibration/chatter). The motor control circuit 102 increases the speed ofthe motor 74 to ensure the cutter 28 efficiently cuts material (e.g.,with uniformity of cut depth and width of unfragmented tissue). In onenon-limiting example, where the motor control circuit 102 communicateswith a PWM circuit, the PWM circuit may increase the duty cycle about50% to 100% or more from its original duty cycle to increase the speedof the motor 74.

In another non-limiting example, the motor control circuit 102 may beconfigured to reduce the power (i.e., current) supplied to the motor 74a predetermined amount, to thereby decrease the speed of the motor ifthe motor control circuit determines that the catheter advancement speedis below a predetermined threshold advancement speed level (asdetermined by the sensor output, for example) for the current rotationalcut speed. For example, the motor control circuit 102 may decrease thespeed of the motor 74 to from about 15,000 rpm to about 7,500 rpm uponmaking such a determination. In such an example, the advancement speedbeing below the predetermined threshold advancement speed level isindicative of the cutter 28 rotating faster than necessary for optimalcutting at the current advancement speed. The motor control circuit 102decreases the speed of the motor 74 to ensure the cutter 28 efficientlycuts material (e.g., with uniformity of cut depth and width ofunfragmented tissue) while reducing fatigue of the drive system by onlyrotating the cutter as fast as necessary for optimal cutting. In onenon-limiting example, where the motor control circuit 102 communicateswith a PWM circuit, the PWM circuit may reduce the duty cycle about 100%to 50% from its original duty cycle to reduce the speed of the motor 74.

Referring to FIG. 17, the motor control mechanism 100 may include anindicator 112 (e.g., an LED) for communicating to the user that themotor control circuit 102 determined that the cutter 28 is being movedinefficiently. In one example, shown in FIG. 18, the indicator 112(e.g., LED) is activated by the motor control circuit 102. In such anembodiment, the motor control circuit 102 may be a microcontroller. Inanother example, the indicator 112 may be a device that provides tactileor audible feedback to the user. Other types of indicators forcommunicating to the user that the cutter is being moved inefficientlydo not depart from the scope of the present invention. In oneembodiment, the motor control circuit 102 may activate the indicator 112to communicate to the user when the cutter 28 is being moved efficientlyand to communicate to the user when the cutter is being movedinefficiently.

In one non-limiting example, the catheter 20 may be configured to allowa user to selectively activate and deactivate the above-describedoperational control function of the motor control mechanism 100. Forexample, if the user wants to use a fixed rotational speed for thecutter 28, regardless of the advancement speed, the user can deactivatethe operational control function of the motor control mechanism 100 toprevent the motor 74 from adjusting the rotational speed of the cutterbased on the advancement speed of the catheter 20. In one example (FIG.12), the handle 34 may include a switch 120 (or other input mechanism)for selectively deactivating or activating the motor control circuit100.

An exemplary flow diagram for the motor control circuit 102 of thepresent embodiment is shown in FIG. 19. In this example, the motorcontrol circuit 102 communicates with the PWM circuit, which includes amicrocontroller for regulating the duty cycle supplied to the motor 74.When the motor control mechanism 100 is active (e.g., such as byactivating the motor control mechanism using the switch 120), themicrocontroller of the PWM circuit sets the duty cycle to an initialduty cycle (e.g., 8000 rpm) at step 130. At step 132, the motor controlcircuit 102 determines, based on the signal from the sensor 104 andduring the cutting operation of the catheter 20, whether the speed ofthe motor 74 is optimal for cutting efficiency based on the advancementspeed of the catheter. In one embodiment, the microcontroller may usecomputer-executable instructions for determining whether the speed ofthe motor 74 is optimal for cutting efficiency based on the advancementspeed of the catheter. For example, in one embodiment themicrocontroller stores data (e.g., a table) specifying an optimalrotational speed of the cutter 28, an optimal amount of power suppliedto the motor 74, and/or an optimal rotational speed of the motor for agiven catheter advancement speed. If the microcontroller 102 determinesthat the speed of the motor 74 is not optimal for the currentadvancement speed of the catheter 20 (for example, by comparing thecurrent amount of power being supplied to the motor to the stored valueof an optimal motor power for the detected advancement speed), then atstep 134 the microcontroller adjusts the amount of power supplied to themotor 74 (i.e., reduces or increases the duty cycle) to adjust the speedof the motor to a level for optimal cutting efficiency at the detectedadvancement speed. For example, if the microcontroller determines atstep 132 that the advancement speed of the catheter 20 (as calculatedbased on the output from the accelerometer) is too fast for the currentrotational speed of the cutter 28, the microcontroller will at step 134increase the duty cycle to increase the rotational cut speed for optimalcutting efficiency at the detected advancement speed. If, for example,the microcontroller determines at step 132 that the advancement speed ofthe catheter 20 (as calculated based on the output from theaccelerometer) is too slow for the current rotational speed of thecutter 28, the microcontroller will at step 134 reduce the duty cycle toreduce the rotational cut speed for optimal cutting efficiency at thedetected advancement speed. At step 136, the microcontroller activatesthe indicator 112 to communicate to the user that the cutter is beingadvanced inefficiently, and that the motor 74 is being (or has been)adjusted in speed based on the current advancement speed. This adjustedspeed mode of the motor 74 is continued until (or unless) an advancementspeed is detected by the sensor 104 that would require a furtheradjustment in the rotational speed of the cutter 28. If themicrocontroller determines that rotational cut speed is the optimalspeed for the current advancement speed of the catheter 20, thendetection of advancement speed of the catheter and comparison to thepredetermined optimal cutting speed for the detected advancement speedis continued at step 140, which may include a delay. Optionally, at step142 the microcontroller activates the indicator 112 to communicate tothe user that the cutter is being advanced efficiently for the currentrotational cut speed. The microcontroller can also include controls fora maximum duty cycle and a stabilization time for setting the restacceleration value. It is understood that the steps involved indetermining whether the rotational cut speed is optimal for the currentadvancement speed and subsequently adjusting the speed of the motor 74may be other than described above. Moreover, these steps may beperformed using analog and/or digital circuits, without the use of amicrocontroller.

The motor control mechanism as described above compensates forinefficient movement of the catheter 20 by adjusting the rotationalspeed of the cutter 28. The rotational speed of the cutter 28 isadjusted to obtain optimal cutting efficiency based on the movement(e.g., advancement speed, vibration) of the catheter 20. This allows auser to advance the catheter 20 at whatever advancement speed iscomfortable while still obtaining a uniform and unfragmented cut pass.The rotational speed of the cutter is not unnecessarily increased (onlywhen inefficiency is determined) to limit fatigue of cathetercomponents.

The order of execution or performance of the operations in embodimentsof the invention illustrated and described herein is not essential,unless otherwise specified. That is, the operations may be performed inany order, unless otherwise specified, and embodiments of the inventionmay include additional or fewer operations than those disclosed herein.For example, it is contemplated that executing or performing aparticular operation before, contemporaneously with, or after anotheroperation is within the scope of aspects of the invention.

Embodiments of the invention may be implemented with computer-executableinstructions. The computer-executable instructions may be organized intoone or more computer-executable components or modules. Aspects of theinvention may be implemented with any number and organization of suchcomponents or modules. For example, aspects of the invention are notlimited to the specific computer-executable instructions or the specificcomponents or modules illustrated in the figures and described herein.Other embodiments of the invention may include differentcomputer-executable instructions or components having more or lessfunctionality than illustrated and described herein.

Having described the invention in detail, it will be apparent thatmodifications and variations are possible without departing from thescope of the invention defined in the appended claims. When introducingelements of the present invention or the preferred embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising”,“including” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements. In viewof the above, it will be seen that the several objects of the inventionare achieved and other advantageous results attained.

As various changes could be made in the above constructions, products,and methods without departing from the scope of the invention, it isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:
 1. A tissue-removing catheter for removing tissue from a body lumen during a cutting operation thereof, the tissue-removing catheter comprising: an elongate catheter body configured for insertion into the body lumen, the catheter body having opposite distal and proximal portions, and a longitudinal axis extending between the distal and proximal portions; a tissue-removing element located generally at the distal portion of the catheter body for rotation generally about the longitudinal axis of the catheter body; an electric motor operably connected to the tissue-removing element for imparting rotation of the tissue-removing element about a rotational axis during the cutting operation of the catheter; a sensor configured to detect a parameter of the catheter body during the cutting operation of the catheter; a motor control circuit in electrical communication with the sensor and the motor, wherein during an operational control function, the motor control circuit is configured to: receive a signal from the sensor based at least in part on the parameter of the catheter body detected during the cutting operation of the catheter, determine whether the received signal is indicative of inefficient movement of the tissue-removing element, and adjust a rotational speed of the tissue-removing element to increase efficiency of the tissue-removing element if the received signal is indicative of inefficient movement of the tissue-removing element.
 2. The tissue-removing catheter set forth in claim 1, wherein the parameter detectable by the sensor is indicative of movement of the catheter body in the body lumen.
 3. The tissue-removing catheter set forth in claim 2, wherein the parameter detectable by the sensor is indicative of an advancement speed of the elongate catheter body in the body lumen.
 4. The tissue-removing catheter set forth in claim 3, wherein if the advancement speed detected by the sensor is greater than a predetermined optimal advancement speed, the motor control circuit is configured to increase the amount of electrical power supplied to the motor to increase the rotational speed of the tissue-removing element.
 5. The tissue-removing catheter set forth in claim 2, wherein the parameter detectable by the sensor is indicative of vibrations of the catheter body in the body lumen.
 6. The tissue-removing catheter set forth in claim 1, wherein the sensor comprises an accelerometer.
 7. The tissue-removing catheter set forth in claim 1, further comprising an indicator in electrical communication with the motor control circuit, wherein the motor control circuit is configured to activate the indicator if the received signal is indicative of inefficient movement of the tissue-removing element.
 8. The tissue-removing catheter set forth in claim 1, wherein the motor control circuit is configured to increase the amount of electrical power being supplied to the motor when the received signal is indicative of inefficient movement of the tissue-removing element.
 9. The tissue-removing catheter as set forth in claim 8, wherein the motor control circuit is in electrical communication with a pulse width modulation (PWM) circuit for said increasing the amount of electrical power supplied to the motor.
 10. The tissue-removing catheter set forth in claim 1, wherein the motor control circuit comprises a microcontroller.
 11. The tissue-removing catheter set forth in claim 1, further comprising a handle connected to the proximal portion of the catheter body, wherein the motor control circuit and the motor are disposed in the handle.
 12. The tissue-removing catheter set forth in claim 11, wherein the sensor is disposed in the handle.
 13. The tissue-removing catheter set forth in claim 11, wherein the sensor is disposed in the distal portion of the catheter body.
 14. A handle for a tissue-removing catheter including a rotatable tissue-removing element for removing tissue from a body lumen during a cutting operation of the catheter, the handle comprising: an electric motor operably connectable to the tissue-removing element for imparting rotation of the tissue-removing element about a rotational axis during the cutting operation of the catheter; a sensor configured to detect a parameter of the tissue-removing catheter during the cutting operation of the catheter; a motor control circuit in communication with the electric motor and the sensor, wherein during an operational control function, the motor control circuit is configured to: receive a signal from the sensor based at least in part on the parameter of the tissue-removing catheter detected by the sensor; determine, during the cutting operation of the catheter, whether the received signal is indicative of inefficient movement of the tissue-removing element; and perform at least one of the following, if it is determined that the received signal is indicative of inefficient movement of the tissue-removing element: adjust a rotational speed of the tissue-removing element, and activate an indicator to communicate to the user that the tissue-removing element is moving inefficiently.
 15. The handle set forth in claim 14, wherein the parameter detectable by the sensor is indicative of movement of the tissue-removing catheter in the body lumen.
 16. The handle set forth in claim 15, wherein the parameter detectable by the sensor is indicative of an advancement speed of the tissue-removing catheter in the body lumen.
 17. The handle set forth in claim 16, wherein if the advancement speed detected by the sensor is greater than a predetermined optimal advancement speed, the motor control circuit is configured to increase the amount of electrical power supplied to the motor to increase the rotational speed of the tissue-removing element.
 18. The handle set forth in claim 17, wherein the motor control circuit is in electrical communication with a pulse width modulation (PWM) circuit for said increasing the amount of electrical power supplied to the motor.
 19. The handle set forth in claim 15, wherein the parameter detectable by the sensor is indicative of vibrations of the tissue-removing catheter in the body lumen.
 20. The handle set forth in claim 14, wherein the sensor comprises an accelerometer. 